Conventionally, a card reader has been widely utilized, which performs reading of magnetic data recorded in a card and recording of magnetic data to the card. In an industry such as a financial institution where a card reader is utilized, illegal acquisition of magnetic data of a card by a fraudulent person who attaches a magnetic head to a card insertion part of a card reader, in other words, so-called skimming has conventionally become a large issue. In order to cope with the issue, a card reader has been proposed, which generates a disturbing magnetic field for preventing reading of magnetic data using a magnetic head for skimming (hereinafter, referred to as a “skimming magnetic head”) (see, for example, Patent Literature 1).
A card reader described in Patent Literature 1 includes: a disturbing magnetic field generator that generates a disturbing magnetic field; a conveying roller that conveys a card inserted through a card insertion port; and a motor that drives the conveying roller. The card reader also includes a magnetic head (pre-head) that detects whether magnetic data are recorded in a magnetic stripe of the card inserted through the card insertion port. In the card reader, when the pre-head detects that the magnetic data are recorded in the magnetic stripe of the card inserted through the card insertion port, the motor is activated to drive the conveying roller. The card is thus taken into the card reader. Also in the card reader, after the activation of the motor, the disturbing magnetic field generator generates a disturbing magnetic field during a period of time in which a rear end side of the card is protruded from the card insertion port.
Patent Literature 1: Japanese Patent No. 3936496
In the card reader described in Patent Literature 1, for the purpose of surely preventing skimming using a skimming magnetic head, the disturbing magnetic field generator generates a disturbing magnetic field before the magnetic stripe of the card inserted through the card insertion port reaches the pre-head and, further, the disturbing magnetic field generator generates a disturbing magnetic field for a predetermined period of time after the magnetic stripe has reached the pre-head. In other words, in the card reader described in Patent Literature 1, for the purpose of surely preventing skimming using a skimming magnetic head, a disturbing magnetic field is also generated at the time when the pre-head reads magnetic data.
According to examinations of the present inventors, however, they have found that, in the card reader described in Patent Literature 1, in a case that a disturbing magnetic field is generated at the time when the pre-head reads magnetic data, an output signal from the pre-head varies owing to the disturbing magnetic field, which makes it difficult for the pre-head to appropriately detect whether magnetic data are recorded in a magnetic stripe. In other words, according to the examinations of the present inventors, they have found that, in the card reader described in Patent Literature 1, it is difficult for the pre-head to appropriately detect whether magnetic data are recorded in a magnetic stripe of a card inserted through the card insertion port, in a state in which a disturbing magnetic field is generated.